(a) Field of the Invention
The present invention relates to a method of pasteurizing in-shell eggs. More specifically in the present invention, yolk and albumen of in-shell eggs are pasteurized separately during the process of a series of pasteurizations of the salmonella (bacteria inhabiting in eggs with shells) by heating it to a desired level, while various temperature measuring points are established within the egg and according to such measuring points, the lowest temperature of the yolk and albumen are measured through the previous pasteurization process. And having this lowest temperature as the standard, the necessary time needed for pasteurization above this lowest temperature is standardized, in order to have the yolk and albumen to be pasteurized simultaneously.
(b) Description of the Related Art
There has been immense research and effort regarding the pasteurization of salmonella—which generally inhabit inside an egg, and in particular, in the case of the liquid egg (liquid white, liquid yolk and liquid whole egg) masses have been produced even commercially since several decades ago. Several nations already hold the standard regarding pasteurizing liquid egg, and its safety has also been substantiated.
The shell egg (its main ingredients being the egg shell, yolk, and the albumen, the egg shell takes up 10˜20%, the albumen takes up 55˜63%, and the yolk takes up 26˜33%), an egg with an egg shell, is not simple to pasteurize due to the complexity of its features, weight, size, form, difference in thermal conductivity and the existence of the egg shell. Moreover, in the commercial front, immense research and effort is attempted regarding pasteurization, and as safety having its priority in quantity and taste serves as a top factor in food consumption of the present, and additionally, as the nations of the global arena stress importance of the safety of livestock from mad cow disease, foot-and-mouth disease, and so forth, there is a demand for the research and interest in the development of shell egg pasteurization.
There are two ways in which the salmonella can be contaminated; one being the contamination into the interior of an egg through the pore of a medium surrounding an egg-laying facility after the egg is laid, and the other being the contamination from the layer before the egg is laid. In the case of the former contact contamination through the pore, it is contaminated due to the fact that generally, eggs possess around 7,00˜17,000 pores for respiration and the salmonella can easily pass through it. In the case of the latter, deeper parts of an egg's yolk and albumen is contaminated due to the contamination of the layer's interior of the body before the egg shell is formed. Both the former and latter are contaminated into the interior of the egg, thus making pasteurization difficult. The most dangerous sort of salmonella being the Salmonella Enteritidis(SE), an egg contaminated with it must be pasteurized in all parts of its interior due to the fact that the Salmonella Enteritidis(SE) contaminates the interior of an egg and deeper into the yolk and albumen inside the egg shell through a layer's internal organs which were already contaminated.
When pasteurizing through heating according to an egg's characteristics (pH concentration, temperature of the interior, weight, size, composition, specific gravity, form, thickness of the egg shell, difference in breed and so forth) and the pasteurization environment (means of heating, heating medium, method of heating, temperature of egg in the early stage and so forth), not only is an egg's temperature different in various locations the temperature amount precedence also changes depending on the time difference. Consequently, the complete pasteurization of the salmonella inhabiting in the egg's interior is difficult.
When pasteurizing an egg through heating, it must be done to the level of safeness as a food product and maintain the quality and distinctiveness of the egg as a food in terms of the yolk and albumen's solidification. Should an egg be pasteurized through heating at a high temperature for an extended time, it is satisfactory in terms of safeness yet is incongruous as a food product with damages in the function and solidification of the albumen and so forth. On the other hand, pasteurization in a low temperature for a short period of time is satisfactory as a food yet incongruous in the sense of safeness, and the pasteurization for a short period of time in a high temperature will damage the egg shell and cause problems in the albumen's ripening and solidification. Moreover, pasteurization in a low temperature for an extended time produces low work efficiency and the gelation, in which the yolk and albumen switch form liquid to solid and thus holds a problem in that it is not easy to pasteurize the shell egg. The shell egg is composed of the egg shell, yolk, and albumen the pasteurization of it is difficult due to the distinctiveness of each material, the solidification by heat and the difference of heat conductivity, the solidification and damage in the function of the yolk and albumen when heated, and the damage of the egg shell and the changes in the condition of the pasteurization when a lapse in the egg laying time affects the albumen's pH concentration.
Much research has been done on the pasteurization of the shell egg and it was thought obvious that when pasteurizing through heating, all parts of an egg had the same temperature, ignoring the fact that they are different, or that the pasteurization of one part of an egg's interior (the center part of the yolk) would sufficiently pasteurize the entire egg. For example, in U.S. Pat. No. 6,165,538, the center of the yolk is set as the standard in determining the pasteurizing time and temperature, and with a presumption that the pasteurization of the center of the yolk will sufficiently pasteurize the entire egg, the pasteurizing conditions are set.
However, when pasteurizing shell egg through heat, the temperatures of the shell egg's interior are different as time goes by according to the condition of the egg, the means of heating and the amount of heating. There are even some instances where the central yolk part's temperature is higher, thus not pasteurizing the yolk's exterior even if the central part of the yolk is pasteurized and the albumen may not be pasteurized even yolk may be pasteurized. Therefore, generally when pasteurizing with a heating medium, the temperature of the yolk and albumen of an egg's interior will be different according to the time and measuring points. This produces the problem of ov r pasteurization and under pasteurization. Moreover, when shifting an egg in two or more heating media, the yolk and albumen's temperature will abruptly fall. In this instance, the central part of the yolk is pasteurized above the arranged pasteurizing temperature but exterior part of yolk breaks away from the arranged temperature without pasteurization. In severe cases, the albumen's temperature fall is more abrupt and while the yolk's pasteurization remains above the arranged pasteurizing temperature, the albumen will not be pasteurized as it has broken away from the arranged temperature.
Therefore, pasteurization of the yolk does not surely ensure the pasteurization of the albumen nor does the pasteurization of a part of or the central part of the yolk ensure the pasteurization of another part of the yolk or entire part of the egg. Due to these problems, the need for pasteurization by having the lowest temperature of the yolk and albumen as the standard in the entire pasteurizing procedure (including the refrigerating process) is prominent.